If you're the person who actually places the order for automotive metal parts — filter cases, spark plug housings, starter-alternator components, clutch kits, EV thermal parts — this checklist is for you.
I've been handling ACDelco and aftermarket parts orders for nine years. In that time, I've personally made 12 significant mistakes, totaling roughly $28,000 in wasted budget. Some of those parts went into recycling bins. Some got reworked. All of them taught me something I now keep in a checklist on my desktop.
This isn't a high-level "make sure you double-check things" post. These are the exact steps we run before every order now.
When to Use This Checklist
Use it when you're ordering replacement or production parts with similar names, similar-looking housings, or multiple vehicle applications. If the part number has letters and digits that look too close to another part number, pause. If the customer says "it's the same as last time" but can't show me a PO, pause. Run this list.
The Five-Point Checklist I Now Run Before Every Automotive Parts Order
1. Match the Part Number, Not Just the Name
Let's start with the one that bit me first. Back in 2018, I received a request for an ACDelco PF633G engine oil filter. The old filter was sitting right there, and it looked exactly like the PF632G I had stocked. Same shape. Same rubber gasket. Almost same thread.
Turns out they're not always interchangeable. The PF633G application depends on the engine, not just the filter size. I ordered based on the visual match, and the thread pitch was wrong for that specific application. The result: 150 filters, $890, straight to the trash. (Note to self: never judge a filter by looking at it.)
Now I write the part number and the VIN or engine code on the same line of the PO. If they don't match, we stop.
2. Understand Rapidfire Spark Plugs vs. Regular Spark Plugs
Here's where marketing can get you in trouble. When a customer asks for ACDelco Rapidfire spark plugs vs regular, they might assume Rapidfire is just a nicer version of the same plug. It isn't always.
Everything I'd read said premium plugs outperform budget ones. For our specific use case — commercial engines with a standard tune — the regular spec is often the safer call. The Rapidfire's different electrode gap and heat range can cause misfires if the engine wasn't designed for it. I learned this after a customer rejected a batch because the gap was pre-set at .045 instead of .040. I'd copied the part number correctly, but I'd "upgraded" the item. That's not what they wanted.
The lesson: specify the exact plug by ACDelco part number, not by "Rapidfire" or "regular." Also, ask about electrode gap before ordering bulk quantities. (I really should have done that on order #1047.)
3. Verify the Starter and Alternator Mounting Details
Several RFQs this year listed "starter alternator" as if it's one combined unit. In most cases, it's not. A starter rotates the engine to start it; an alternator charges the battery. Hybrid vehicles sometimes use an integrated starter-generator, which is still a different housing.
The classic mistake: ordering the right rotating electrical part but the wrong mounting flange. On a $3,200 order for alternator front housings, I missed that the customer needed the 12V version with a 2-bolt mount, not the 3-bolt one. The dimensional drawing was right there. The drawing note said "2 bolt" in tiny text. I approved it anyway.
Now I always require a photo of the old unit and a clear view of the mounting holes. If the customer can't provide one, they get the supplier's dimensional drawing and have to sign off before the order moves to production.
4. Confirm the EVO Clutch Kit Generation and Spline Count
EVO clutch kit sounds pretty specific, right? It's not. There are big differences between EVO generations, not just in the clutch cover but in the input shaft spline count. A CT9A order isn't the same as a CZ4A order. I once ordered a batch based on "EVO clutch kit" and a year range. The spline count was wrong. Every item had to be reworked.
The fix is simple: include the chassis code or engine code and the disc spline count on the PO. If the supplier asks for clutch dimensions, don't treat that as an insult to your knowledge. Treat it as a sign they know what they're doing.
That mistake cost about $450 in redo plus a 3-day production delay. Not fatal, but completely avoidable.
5. Clarify Electric Radiator vs. Space Heater Components
This one feels silly until you have to explain it to your own manager. In EV and hybrid thermal systems, an electric radiator is usually part of the cooling loop — it dissipates heat from the battery or power electronics. A space heater in vehicle terms is usually a PTC heater that warms the cabin. They're both heat exchangers. They're not the same part.
Last September, I wrote "electric radiator" on a quote for what the customer actually needed as a passenger-compartment heater core. The parts looked familiar enough that I didn't catch the difference. The customer caught it at inspection, and we had to build a whole new sample run.
So now, for any thermal part, we ask three questions: Is it for battery cooling, power electronics, or cabin heating? What voltage does it run at? And does the connector face forward or sideways? (That last one cost us a 1-week delay once.)
Common Mistakes to Avoid When Using This Checklist
Here's what usually goes wrong even after I hand people this checklist:
- They skip step 1 because the part "looks the same." The PF633G case is empty now, so I keep it on my desk to remind me that looking the same isn't the same.
- They trust the catalog screenshot but don't verify the date. Supplier catalogs change. As of January 2025, we only accept catalog PDFs that include a revision date.
- They trust the supplier's "all good" email without asking for a dimensional report. On production parts, we now require a PPAP submission per AIAG guidelines. That report has caught two wrong flange patterns before they became bad inventory.
I have mixed feelings about all these rules. Part of me wants to trust the team and move faster. Another part knows that every time I've skipped a step, a callback came within two weeks. So we keep the checklist, and it works.
We've caught 47 potential errors with this checklist in the past 18 months. That's 47 times something didn't become a $3,200 headache. I made those mistakes so you don't have to. Use the list.
